Honduras Pine Spacing Trial Results in Puerto Rico

Abstract

Abstract Puerto Rico has one of the oldest, continuously measured spacing trials of Honduras pine (Pinus caribaea mor. hondurensis) in existence. At 18 to 20 years, mean survival for all the trial sites except one that suffered hurricane damage in 1979 was 82%. Survival was not related to the triangular spacing treatments of 5, 7, 10, and 14 feet. But spacing did influence diameter growth at all four sites and affected height growth at all but one site Each site had trees ≥100 feet tall at 18 to 20 years; on the two best sites, individual trees reached 90 feet by 12 years. At close spacings, mean annual height increments peaked at 4.0 to 4.5 years on two sites and at 7.2 years on the other two sites. Mean annual diameter increments peaked even earlier, at 3.0 to 3.5 years on the two good sites and at 6.0 years on the two poorer sites. Early effects of competition in reducing both mean annual height and diameter growth, particularly at close spacings, have several managerial implications. The most striking are: (1) underestimating site quality or site index if growth assessments are made only in dense stands, and (2) significant loss of wood volume over long rotations when managers fail to time thinnings before mean annual height and diameter increments decrease.